Optical fiber event sensor

ABSTRACT

A micro pH sensor is constructed by reacting powdered aminoalkylated cellulose with a dye to covalently bond the dye to the aminoalkyl groups on the cellulose. Any excess unreacted aminoalkyl groups are blocked with a blocking agent and the dye containing powdered cellulose is taken up in a solvent. A portion of the solvated dye containing cellulose is deposited in association with an optical fiber. The cellulose is regenerated into a solid matrix by acid treatment of the solvated dye containing cellulose to deposit the dye containing celllulose matrix on the optical fiber.

This application is a division of application Ser. No. 917,913, filed10/10/86 U.S. Pat. No. 4,798,738.

BACKGROUND OF INVENTION

This invention is directed to an event sensor, as for instance a pHsensor and a process for the preparation of such a sensor. The sensorutilizes a dye which is sensitive to an event. The dye is attached to afinely divided polymeric material as for instance cellulose. Thepolymeric material, bearing the dye thereon, is dissolved in a solventand is deposited on an optical surface of an optical fiber. Thepolymeric material, bearing the dye, is regenerated from the solution toform a solid matrix of the polymeric material, bearing the dye, on theoptical surface of the optical fiber.

The determination of an event, as for instance the hydrogen ionconcentration or pH of a solution, is very important in many situations.One of theses is the determination of the pH of biological specimens, asfor instance, blood. The pH of the blood is indicative of manyphysiologically important conditions of a patient.

In constructing event sensors it is necessary to construct them of amaterial which is permeable to an indicator of the event being measured.For a pH sensor, the material must be permeable to ionic species. Thisseverely limits the types of material which may be used for suchsensors.

Glass pH electrodes have been used for years for pH determinations.These glass electrodes have to be dipped into a solution fordetermination of the pH of the solution. In a medical situation, such asa patient recovering from a myocardial infarction, it would beadvantageous to be able to measure the pH event in real time, that iscontinuously. Unfortunately this is not possible with glass electrodes.With glass electrodes, at best, only intermittent measurements can bemade. Each of the seperate measurements requires withdrawal of analiquot of blood from the patient and sending the blood sample to thelaboratory for the determination of the pH of the patient's blood. Asidefrom the requirement of having to continuously withdraw the aliquots ofblood, this procedure is time consuming and as such it does not give atrue reflection of the patient's condition in real time.

For biological fluids, a prior known sensor uses the fluorescentproperties of a dye in conjunction with the ionic permeability of apreformed integral cellulose membrane sheet. In this sensor, thecellulose membrane is chemically treated so as to introduce covalentbondable groups onto the membrane. The dye is then covalently bonded tothese groups to adhere the dye to the membrane. A small disk is cut fromthe membrane sheet and is attached to a cassette in association with anoptical fiber bundle also attached to the cassette. When the dye isexcited by excitation light imposed on the dye along the fibers, itunder goes fluorescence, emitting a wavelength of light at a differentwavelength than the excitation wavelength. The emission light ismeasured as an indication of the pH.

In constructing the above sensor, it is important to insure that the dyeis evenly distributed across the membrane sheet such that there will bereproducibility between individual disks cut from the membrane sheet.Aside from evenly disbursing the dye molecules across the membrane, itis also important to insure that the dye molecules are placed withrespect to one another such that there is a sufficient concentration tobe responsive to pH changes in the solution being measured. Because ofthese considerations, it is necessary to perform quality controlprocedures on each disk cut from the membrane to insure that thedistribution of the dye on the cellulose membrane is sufficient torender the individual disk useful as a pH sensor.

The above noted cellulose membranes utilize a commercial cellulosemembrane as for instance a cellulose membrane suitable for use as adialysis membrane. The intact membrane is first treated with cyanogenbromide followed by a condensation with an appropriate amine, forinstance hexamethylenediamine. This yields a compound which has aprimary amino functional group which is reacted with the dye, to attachthe dye to the membrane. This method does not lend itself easily to thefabrication of a microsensor on an optical fiber tip which is on theorder of 0.006 inches in diameter.

BRIEF DESCRIPTION

This invention provides a micro sensor for sensing an event such as apH. The sensor of the invention is capable of being constructed in asize of the size domain of an optical fiber. The sensor of the inventionis capable of being easily and inexpensively manufactured.

This can be advantageously accomplished by providing a process offorming a micro sensor which comprises selecting a quantity of finelydivided water insoluble ionic permeable hydrophylic polymer having aplurality of attachment sites thereon and reacting the attachment siteson the polymer with a quantity of an event sensitive dye so as to attachthe dye to at least some of the attachment sites on the polymer to forma dye bearing polymer. The dye bearing polymer is then dissolved in asolvent. A quantity of the solvated dye bearing polymer is thendeposited onto an optical surface of an optical fiber and the dyebearing polymer is regenerated from the solvent to form a solid matrixof the regenerated dye bearing polymer on the optical surface of theoptical fiber.

In an preferred embodiment, the micro sensor is a pH sensor, the polymeris powdered cellulose and the attachment sites on the cellulose comprisesubstituent groups on the cellulose. The dye is attached to at leastsome of the substituent groups on the cellulose to form a dyesubstituted cellulose. The event sensitive dye is chosen to be a pHsensitive dye. The dye can be attached to the substituent groups on thecellulose by covalently bonding the dye to at least some of thesubstituent groups on cellulose. Further essentially any substituentgroups on the cellulose not having the dye attached thereto can bereacted with a blocking agent so as to render the blocked substituentgroups essentially pH insensitive.

In an illustrative embodiment, the substituents groups on the celluloseare C₂ -C₂₀ aminoalkyl groups and the dye is attached to the aminoalkylgroups on the cellulose by covalently bonding the dye to at least someof the aminoalkyl substituents on the cellulose. Essentially anyremaining aminoalkyl groups on the cellulose not having the dye attachedthereto can be blocked by reacting with a blocking groups so as torender the blocked aminoalkyl groups essentially pH insensitive. Theblocking can be accomplished by reacting with an acylating agent such asan acetylating agent.

In an illustrative embodiment the dye is hydroxypyrenetrisulfonic acidor an acceptable salt thereof such as a physiological acceptable salt.This dye is a known dye for use in sensing pH. The dye can besubstituted onto the cellulose by reacting the hydroxypyrenetrisulfonicacid to form at least a mono-sulfonyl chloride derivative of thehydroxypyrenetrisulfonic acid and reacting the mono-sulfonyl chloridewith the aminoalkylcellulose to attach the dye to the cellulose byforming sulfonamide linkages between the dye and theaminoalkylcellulose. The aminoalkyl cellulose can beaminoethylcellulose.

In an illustrative embodiment, the process can be enhanced by adding aquantity of a permeability enhancing agent to the solution of the dyecontaining cellulose. The permeability enhancing agent would be selectedfrom small molecular weight water soluble hydrophilic compounds such assugars, polyols and the like. Suitable for the permeability enhancingagent is glycerol.

When cellulose is used for the polymer it can be regenerated by acidtreating the deposited quantity of the solvated dye substitutedcellulose located on the optical fiber. This can be accomplished bydipping the deposit of the solvated dye bearing cellulose on the end ofthe fiber into an acid bath. To enhance the ionic permeability of thesensor, a quantity of glycerol can be added to the acid bath prior todipping the solvated dye bearing cellulose into the bath.

An illustrative process for forming a pH sensor comprises selecting aquantity of powdered cellulose having a plurality of substituentaminoalkyl groups thereon, reacting the aminoalkyl groups on thecellulose with a quantity of a pH sensitive dye so as to covalently bondthe dye to at least some of the aminoalkyl groups on the cellulose toform a dye substituted cellulose, dissolving the dye substitutedcellulose in a solvent and depositing a quantity of the solvated dyesubstituted cellulose onto an optical surface of an optical fiber, andthen regenerating the dye substituted cellulose from the solvent by acidtreating the deposited quantity of the solvated dye substitutedcellulose on the optical fiber to form a solid matrix of regenerated dyesubstituted cellulose on the optical fiber.

In any of the embodiments of the invention the solid matrix of theregenerated dye bearing polymer, as for instance a cellulose matrix, canbe coated with an overcoating. This overcoating would cover the matrixand might extent down over a portion of the optical fiber which isimmediately adjacent to the solid matrix.

An advantageous event sensor of the invention includes (a) an opticalfiber having an optical surface, (b) a matrix of regenerated polymericmaterial formed in situ on the optical surface of the optical fiber bydepositing a droplet of the polymeric material in solution in a carriersolvent on the fiber and regenerating the polymeric material from thesolution by treating the carrier solvent with a regeneration reagent toform the matrix of the polymeric material on the fiber, and (c) aplurality of even sensing dye groups attached to the polymeric material.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood when taken in conjunction withthe drawing wherein:

FIG. 1 is cross sectional view of an event sensor of the invention.

This invention utilizes certain principles and/or concepts as are setforth in the claims appended to this specification. Those skilled in thesensor arts will realize that these principles and/or concepts arecapable of being utilized in a variety of embodiments which may differfrom the exact embodiments utilized for illustrative purposes herein.For these reasons, this invention is not to be construed as beinglimited to only the illustrative embodiments but should only beconstrued in view of the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The improved microsensors of the invention are constructed so as to havea even dispersion of a dye throughout a supporting polymeric material.The dye is initially bound to a divided polymeric material. Thismaterial is then taken up in solution and a drop of the solution isdeposited on an optical surface of an optical fiber. The polymericmaterial is then regenerated into a solid, forming a matrix on theoptical surface of the optical fiber. Dispersed in the matrix is thedye. This allows for the creation of a microsensor having the dye evenlydispersed throughout the matrix of the supporting material.

By utilizing a finely divided polymer and attaching the dye to thisfinely divided polymer, the finely divided polymer can then be mixed orotherwise homogenized to insure that the dye is evenly dispersedthroughout the polymer. This allows for portions of the polymer to beutilized at different instances of time while only requiring a singlequality control test on an aliquot of the batch.

In the preferred form of the invention a micro pH sensor is constructed.In order to determine the pH of a solution, as for instance a bloodsolution, it is important that the supporting polymeric material bewater insoluble, such that it is not degraded by the test solution whosepH is being determined. Further it has to be permeable to ions in orderfor ions from the test solution to cross through the polymer andinteract with an appropriate dye located within the interior of a matrixof the polymer.

A further characteristic of the polymer once it has the dye attachedthereto is that it must be solubilized so as to be transferable to anoptical surface of an optical fiber. Once the polymer with the dyeattached thereto is solubilized, a small aliquot of the solution of thepolymer with the dye attached thereto can be located on the opticalsurface of the optical fiber. Regeneration of the solid polymer from thesolution then yields a solid matrix of the polymer having the dyelocated therein, which is correctly positioned on the optical surface ofthe optical fiber.

The polymer is chosen to be a water insoluble, ionic permeable polymer.Macromolecular hydrophilic polymers which have these generalcharacteristics are useful. Such polymeric material would includecellulose, high molecular weight polyvinylalcohol, (i.e. PVA),polyurethanes, polyacrylamides, polyhydroxyalkyl acrylates, polyvinylpyrrolidones, hydrophilic polyamides, and polyesters. Generally, for pHsensors, cellulose and high molecular weight polyvinylalcohol wouldprimarily be considered. The polyvinylalcohol would be chosen such thatits molecular weight is sufficiently high to render it water insoluble.Solubilization of the polyvinylalcohol would be accomplished via amixture of water/alcohol as would be appropriate for the particularpolyvinylalcohol utilized.

Coupling of the dye to the polymeric material can be accomplished eitherby direct coupling of the dye to reactive sites on the polymericmaterial, as for instance, hydroxyl group on either cellulose orpolyvinyl alcohol, or through indirect coupling utilizing a substituentgroup which in itself is coupled to the polymeric material. As, forinstance, alkylamines could be first joined to the polymeric material.Thus, for cellulose, an alkylamine would be joined to a hydroxyl groupon the cellulose backbone by forming an ether between the alkyl portionof the alkylamine and cellulose backbone. This leaves the aminofunctionality of the alkylamine available for reaction with the dye tojoin the dye to the polymeric matrix or backbone.

While the dye could be joined to the polymeric material either directlyor through a substituent group utilizing secondary bonding techniquessuch as hydrogen bonding or the like, it is preferred to form a covalentbond between the dye and the attachment point, either directly on apolymeric material or indirectly through a substituent group. Thisassures that the dye is fixedly and irreversibly bound to the polymericmaterial for improved performance of the sensor.

If less than all of the substituent groups are reacted with the dye, thesubstituent group would be chosen such that either it will not interferewith the measurement being taken or any unreactive substituent groupused are capable of being blocked. For instance, if cellulose isutilized and an aminoethyl group is used as the substituent group andthe concentration of the dye was chosen such that less than all of theaminoethyl groups are reacted with the dye, the remaining aminoethylgroups are appropriately blocked as, for instance, with an acyl blockinggroup to essentially neutralize any charge on the unreacted amino groupssuch that they do not interfere with the measurement being taken, as forinstance, a pH measurement.

Generally, suitable for the substituent groups would be C₂ to C₂₀aminoalkyls. These aminoalkyl groups could be straight chain, branchedchain, cyclo or aromatic. They could include substitution groups locatedthereon which are hydrophilic such as --OH, --NO₂, carboxyl, sulfonateor the like. Generally the aminoalkly group will be C₂ to C₈ with the C₂and C₃ aminoalkyl groups being preferred, i.e, aminoethyl oraminopropyl. For ease of blocking of any excess aminoalkyl groups,acetyl can be chosen as a convenient blocking group.

The above noted acyl blocking groups are conveniently utilized forblocking functional groups such as amino groups. Other blocking groupscould be utilized to block such amino groups or other functional groupsas long as they convert a chargeable species such as the basic aminospecies of the amino group to a neutral species such that if the sensoris being utilized as a pH sensor, any basic or acidic properties of thesubstituent groups do not interfere with the pH measurement.

Generally, the starting material for the matrix will be a solid, finelydivided polymeric material, as for instance, a powdered material.However, as will be apparent to the art skilled, a different state, asfor example a liquid material, could be initially utilized, reactingwith the dye and further treated so as to be able to form a solid statematerial once the dye bearing polymeric material is located on theoptical surface of an optical fiber. For convenience however,utilization of a solid powder polymeric material is preferred.

The dye can be added to the polymeric material utilizing either a solidstate reaction or a solution reaction. In any event, once the dye isadded to the polymeric material, the state of this dye bearing polymericmaterial should be such that a homogeneous mixture can be formed. Asopposed to prior use of membrane sheets which tend to haveinconsistencies across the surfaces of the membrane sheet resulting inuneven concentration of the dye on the membrane, by utilizing apolymeric material in a state which allows for homogenization of the dyebearing polymeric material, homogenous properties in the final eventsensor can be obtained.

The dye will be chosen such that it is either an absorption dye or afluorescent dye. For use with a pH sensor, dyes such ashydroxypyrenetrisulfonic acid or its salts, fluorecein orbeta-methylumbelliferone can be utilized. These dyes are all very usefulfor the physiological pH range of blood, as for instance, from about 7.0to about 8.0. It is recognized that other pH ranges might be chosen as asensing pH range, or other events other than pH sensing might be chosen.For these other pH ranges or other events, appropriate dyes which areindicative of these events would be chosen, as for instance, if a lowerpH range was to be measured, a dye having characteristics of that lowerpH range would be chosen.

As noted above, the polymeric material must be susceptible totransmitting ionic species across it such that these ionic species canreact with the dye. If a pH sensor is constructed, the pH within thematrix of the sensor itself may not be exactly the same as the pH of thetest solution, but it will be such that it tracks the pH of the testsolution. Thus, as the pH of the test solution goes up, so does theinternal pH within the sensor and as the pH of the test solution goesdown, so does the internal pH within the matrix of the sensor.

Once the dye is located on the polymeric material, followed by blockingof any reactive substituent groups or any other groups on the polymericmaterial if desired, the dye bearing polymeric material is thensolubilized in a suitable solvent. The solvent of choice will dependupon the polymeric material itself. In any event, upon solubilization ofthe dye bearing polymeric material, further homogenization of the dyebearing material takes place by virtue of the solubilization procedureitself.

An appropriate aliquot of the solubilized dye bearing polymeric materialis then loaded onto an optical surface of an optical fiber. Thesolubilized polymeric material is then regenerated so as to form a solidmatrix of the dye bearing polymeric material on the optical surface ofthe optical fiber. Regeneration would depend upon the polymeric materialand its solvent. As per the illustrative examples herein, for use withcellulose, a convenient regeneration method is acid regeneration of thecellulose. This is easily accomplished and is easily facilitated formanufacturing reasons by simply adding a drop of a fairly viscoussolution of the cellulose material onto the optical surface on the endof an optical fiber and dipping that end of the optical fiber into anacid bath. This regenerates the cellulose matrix forming a solid matrixof the dye bearing regenerated cellulose on the end of the fiber. Thisis much easier than attempting to adhere a preformed disk or matrix onthe very small end of an optical fiber.

If desired, additional solubilized polymeric material can be added tothe existing regenerated material already on the optical surface of anoptical fiber. The further addition is followed by a furtherregeneration acid dip. This allows for the build up of a final matrix ofa precise dimension. Since the solubilized cellulose adheres to both theregenerated cellulose matrix and to the glass of the optical fiber, itis possible to repeatedly add new aliquots of solubilized cellulose ontothe existing regenerated cellulose to stepwise build up a sensor of anydesired dimension.

For an illustrative pH sensor of this invention, cellulose will beutilized as the polymeric material. Aminoethylated cellulose iscommercially available in a powdered form, as for instance for SigmaChemical, St. Louis, MO. Normally if commercial aminoethylcellulose isutilized, the material as received from the manufacturer will be firsttreated to generate free amine groups. This is easily accomplished bysimply treating with a sodium bicarbonate solution and drying. Theactivated aminoethylcellulose should be protected from CO₂ in theatmosphere in order to prevent formation of carbonate salts ofaminoethylcellulose.

The aminoethylcellulose is then treated with an appropriate dye. For thepurposes of illustration of a pH sensor of this invention,hydroxypyrenetrisulfonic acid will be utilized as the dye. It is ofcourse realized that this material could be used as the free acid or asa suitable salt as, for instance as alkali or an alkali earth salts. Foruse directly within a patient, physiological acceptable salts such thesodium, potassium, calcium or magnesium salts would be used. In anyevent, the hydroxypyrenetrisulfonic acid hereinafter referred to as HPTSfor brevity of this application is first converted into an activespecies. For use with aminoethylcellulose or other aminoalkylcellulose,a suitable active species would be a sulfonic acid chloride. The HPTS isfirst acetylated to protect the hydroxy function of the HPTS and then itis converted to a suitable acid chloride. Normally for HPTS, thisreaction with aminoethylcellulose will be conducted to yield the monosubstituted HPTS.

The acid chloride derivative of the HPTS is reacted withaminoethylcellulose to covalently bond the dye to the cellulose backbonematerial utilizing sulfonylamido linkages. As is evident from thereaction of an acid chloride with an amine, hydrochloric acid isgenerated as a byproduct. This byproduct hydrochloric acid tends toreact with other amine groups on the aminoethylcellulose. In view ofthis, the dye can be stepwise reacted with the aminoethylcellulose byfirst treating with a first batch of the HPTS acid chloride followed bytreating this product to convert any amino hydrochlorides back to thefree amine groups, and further reacting with additional HPTS acidchloride. It is evident that the desired amount of dye which is to beloaded onto the cellulose can be controlled by either stoichiometriccontrol of the amount of dye which is in fact added to any particularamount of cellulose or by stepwise control by repeated treatments addingfirst one molecule of the dye and concurrently generating an aminehydrochloride on a further amine group, effectly blocking it againstreaction with the dye, followed by regeneration of the free amine fromthe amine hydrochloride and then adding a second dye group. It is, ofcourse, realized that this could be repeated as many times as isnecessary to add increasing amounts of the dye to theaminoethylcellulose.

Once the desired amount of dye is added to the aminoethylcellulose anyremaining amino groups are blocked so as to prevent free primary aminesfrom interfering with the pH measurement of the pH sensor. This can beconveniently done by acylating these amines, for instance by utilizingan acetyl blocking group. During acylation a further basic material, forinstance pyridine, may be present.

Once the dye has been loaded onto the cellulose, the dye bearingcellulose is then taken up into solution. With cellulose, three basictypes of solutions can be formed. The first of these are based oninorganic complexes, the second is based upon organic complexes and thethird utilizes hemi esters or sulfur complexes.

For forming inorganic solvents, generally metallic ions such as zinc,copper, nickel, iron, cobalt or cadmium would be utilized. These can beutilized in conjunction with other liquids such as aqueousethylenediamine.

Typical inorganic solutions for solubilizing a dye bearing cellulosemight be copper hydroxide in concentrated ammonia, copper hydroxide inaqueous ethylenediamine, cobalt hydroxide in aqueous ethylenediamine,nickel hydroxide in aqueous ethylenediamine, cadmium hydroxide inaqueous ethylenediamine, nickel hydroxide in concentrated ammonia oriron tartrate in alkali hydroxide.

Typical organic solvents for solubilizing dye bearing cellulose might by161/2% methylamine in dimethylsulfoxide, N-methylmorphine N-oxide orquaternary ammonium bases. Suitable hemi esters or half esters would bea hemisuccinate. Suitable complex sulfur intermediates would be theviscose process, dimethylsulfoxide plus carbon disulfide plus an amineor sulfur dioxide in an amine system.

For all of the above solvents the cellulose can be regenerated by acidtreatment. Such acid treatment typically would entail utilizing adiluted acid such as the common mineral acids, as, for instance,sulfuric acid.

For increased ion permeability of the final polymeric matrix on the endof the optical fiber, permeability enhancing agents can be added. Thesegenerally will be added either in the solvent for the polymericmaterial, the regeneration solution for the polymeric material or bothof these. Suitable for such permeability enhancing material are smallmolecular weight molecules which are hydrophilic and are water soluble.Such compounds might include sugars and polyol and the like. Forinstance, glycerol can be added to both a solvent solution for thecellulose and to an acid regeneration bath. Another specific suitablepermeability enhancing agents would be low molecular weight watersoluble PVA.

After regeneration of the polymeric material on the optical fiber, thedye bearing matrix of the polymeric material on the optical fiber can beovercoated with a suitable coating or overcoating material serving toenhance certain properties of the sensor. An overcoat material would bechosen so as to be ionic permeable as is the polymeric matrix. Suitablefor an overcoating material would be cellulose which is impregnated withcarbon black or the like.

In use, the sensor on the end of an optical fiber is positioned in theappropriate test solution. If a fluorescent dye is utilized, anexcitation light wavelength from a light source is channeled down thefiber toward the sensor. The light strikes the dye, the dyes fluorescesand emits an emission light wavelength. Interaction of the eventindicator with the dye modulates the fluorescence. The emission light isthen channeled back up the fiber to a light sensor for electricalreadout of the same. This procedure is similar to that described inLubbers et al, U.S. Pat. No. 31,879 and Heitzmann, U.S. Pat. No.4,557,900. For brevity of this specification, reference is made to thesepatents for details of this procedure. For this reason, the entiredisclosures of Lubbers et al, U.S. Pat. No. 31,879 and Heitzmann, U.S.Pat. No. 4,557,900 are herein incorporated by reference.

To avoid light intensity changes caused by factors other thaninteraction of the event indicator with the dye, the overcoat is chosento be opaque to the excitation and emission light wavelengths.

FIG. 1 shows a suitable physical sensor 10 of the invention. An opticalfiber 12 is connected to an appropriate light transmitting apparatus 14.The light transmitting apparatus 12 generates the excitation lightλ_(ex). The optical fiber 12 is also connected to a light receivingapparatus 16. The light receiving apparatus 16 receives and analyzes theemission light λ_(em) from the fluorescent dye as is described in theabove referenced Lubbers et al and Heinzmann patents.

Located on the optical surface 18 of the fiber 12 is a dye bearingpolymeric matrix 20, as for instance, a cellulose matrix containing HPTSas a fluorescent dye therein. The matrix 20 adheres to the opticalsurface 18 and slightly down along the sides 22 of the end of the fiber12. An overcoating 24 can then be applied over the totality of thematrix 20 and down further along the side 22 of the fiber 12.

In use, the optical fiber 12 bearing the matrix 20 and the overcoat 24thereon is placed in an appropriate solution. Excitation light of anappropriate wavelength from the light transmitting apparatus 14 is fedto the fiber 12. This interacts with the dye in the matrix 20 causingthe dye to fluoresce. The emission light from the fluorescence is fed tolight receiving apparatus 16.

The sensor 10, as is evident from FIG. 1 is of a size domainapproximately that of the optical fiber 12. Thus, typically, the sensor10 would only be slightly larger than a typical 125 micron diameterfiber. The thickness of the matrix 20 would be chosen so as to beapproximately three to four mils (0.004 inches) thick.

The following is given as a typical preparation of an event sensor ofthe invention. For illustrative purposes, a pH sensor utilizingcellulose as the polymeric material and HPTS as the dye will beutilized.

EXAMPLE 1 Activated Aminoethylcellulose

5 grams of aminoethylcellulose is suspended in 100 mls of 2.5% sodiumbicarbonate solution. It is stirred for 30 minutes, filtered and rinsedwith 50 mls of deionized water. The filter cake is then suspended in 50mls dry dimethylformamide. It is then filtered and again resuspended indry dimethylformamide. This dehydrates the filter cake of the activatedaminoethylcellulose. If the product is not being utilized immediately,it is stored dry, protected from atmospheric carbon dioxide.

EXAMPLE 2 Acetoxy-pyrenetrisulfonic Acid Trisodium Salt

10 grams of trisodium hydroxypyrenetrisulfonate, 50 mls of aceticanhydride and 1.6 grams of sodium acetate are added to 200 mls ofdimethylformamide in a 500 ml flask. The flask is equipped with acondenser having a drying tube and a stirring bar. The contents of theflask are stirred at 50° to 70° C. for one to two hours. The reactionmixture is filtered and the filtrate collected. The filtrate is vacuumevaporated to yield a crude solid product. This crude solid product isextracted into boiling methanol. The volume of the methanol is reducedto 100 mls and cooled. The first batch of product crystallizes out andis filtered. The methanol is again reduced to approximately 20 mls toyield a second crop of product. This is filtered and combined with thefirst batch and dried for twenty to forty minutes at 60° C.

EXAMPLE 3 Acetoxy-pyrenetrisulfonic Acid Chloride

2 grams of trisodium acetoxy-pyrenetrisulfonate from Example 2, above,and 6.6 grams of phosphorous pentachloride (PC1₅) are ground togetherwith a mortar and pestal for 10 minutes. The homogeneous solid mixtureis then transferred to a 250 ml round bottom flask fitted with acondenser and drying tube. It is heated in boiling water for 60 minutes.The reaction mixture is then extracted with 200 mls of hot toluene andvacuum filtered. The toluene from the filtrate is stripped off torecover the acetoxy-pyrenetrisulfonic acid chloride.

EXAMPLE 4 HPTS Bearing Aminoethylcellulose

100 mg of acetoxy-pyrenetrisulfonic acid chloride from Example 3 isadded to 100 mls of dry dimethylformamide. This is stirred for 45minutes and 5 grams of activated aminoethylcellulose is added. Thismixture is stirred for one hour, filtered and the filter cake washedwith 50 mls of dimethylformamide. The filter cake is resuspended in 100mls of 2.5% sodium bicarbonate solution and stirred for 30 minutes. Itis filtered and the filter cake washed twice with 50 ml portions ofdeionized water. The water is then removed from the filter cake by threewashings with dry dimethylformamide. The dried filter cake is thenretreated a second time in 100 mls of dimethylformamide with 100 mg ofacetoxy-pyrenetrisulfonic acid chloride for 45 minutes. After the secondtreatment it is filtered and the cake washed with 2.5% sodiumbicarbonate followed by two water washes. The product is stored over adessicant under high vacuum to dry to same.

EXAMPLE 5 Acetylation of Excess Amino Groups on HPTS Bearing Cellulose

3 to 6 grams of the product from Example 4 with 75 mls of aceticanhydride and 1 ml of pyridine is heated one hour at 60° C. The reactionis cooled and filtered. The filter cake is washed with 50 ml portions ofsodium bicarbonate solution and then three washes with water. It isdried over a dessicant at high vacuum.

EXAMPLE 6 Inorganic Zinc Based Cellulose Solvent

An inorganic zinc based solvent is prepared by dissolving 4.15 grams ofzinc chloride in 100 mls of water. 50 mls of 2.2M sodium hydroxidesolution is added dropwise with stirring over ten minutes. The resultingproduct is centrifuged at 2,000 RPMs in a Beckman TO-6 Centrifuge forten minutes. The supernatant is decanted and 50 mls of 0.5M sodiumhydroxide is added to the precipitate. This is agitated with a glassrod, recentrifuged and decanted again. This procedure is repeated twicemore. 50 mls of cold 40% aqueous ethylenediamine and 1 gram of glycerolare added to the final precipitate. This is mixed together by shaking.The product is then blanketed with nitrogen and stored in arefrigerator.

EXAMPLE 7 Solvated HPTS Bearing Cellulose

0.1 gram of acetylated dye bearing aminoethylcellulose from Example 5above is dissolved by mixing with 1.9 grams of the final solution fromExample 6, above, and stored protected from atmospheric carbon dioxidein a freezer overnight. After standing overnight a viscous solutionresulted. The solution is further maintain in the freezer until used.

EXAMPLE 8 Regeneralted Cellulose pH Sensor

1 drop of the mixture of Example 7 is added to the end of a clean fibertip of an optical fiber. This is dipped into a 5% sulfuric acid, 5%glycerol solution for 5 minutes to regenerate the cellulose. The fiberhaving the regenerated cellulose matrix located thereon is then rinsedwith 1% sodium bicarbonate, 5% glycerol solution for 30 seconds. Thethickness of the sensor is then measured wet. The desired thickness is 3to 4 mils when wet. If the sensor is not of the desired thickness, afurther drop of the product of Example 7 is added and the sensor is onceagain dipped into the sulfuric acid, glycerol bath. The sensor is onceagain washed with sodium bicarbonate and the thickness measured. Afurther amount of the sensor matrix can be regenerated on the sensor if,again, the desired thickness has not been reached.

Generally the dye will be utilized in a ratio of from about 1 mg of dyeto about 20 mg of dye per 1 gram of cellulose. At about 10 mgs of dyeper 1 gram of cellulose, a dye molecule is attached to about 5% of theaverage NH₂ sites on the cellulose.

We claim:
 1. An event sensor which comprises:an optical fiber, saidoptical fiber having an optical surface; a matrix of a regeneratedpolymeric material; a plurality of event sensing dye groups, said eventsensing dye groups chemically bound to said polymeric material; and saidmatrix of said regenerated polymeric material formed in situ on saidoptical surface of said optical fiber.
 2. An event sensor of claim 1wherein:said event sensing dye groups are covalently bound to saidpolymeric material, and said matrix of said regenerated polymericmaterial is formed by depositing said polymeric material in solution ina carrier solvent on said optical fiber and regenerating said polymericmaterial from said solution to form said matrix on said optical fiber.3. An event sensor of claim 2 wherein: said polymeric material iscellulose; and said polymeric material is regenerated by contacting saidsolution on said optical fiber with an acid solution.
 4. At event sensorof claim 3 further including:a plurality of substituent groups locatedon said cellulose; and each of said plurality of event sensing dyegroups covalently bound to said cellulose by covalently bounding each ofsaid event sensing dye groups to one of said substituent groups.
 5. Anevent sensor of claim 4 wherein:said dye is a pH sensitive dye; and saidevent sensor is a pH sensor.
 6. An event sensor of claim 1 furtherincluding:a plurality of substituent groups located on said polymericmaterial, each of said plurality of event sensing dye groups chemicallybound to said polymeric material by chemically bonding each of saidevent sensing dye groups to one of said substituent groups; and aplurality of substituent group blocking groups, said plurality ofsubstituent group blocking groups located on said substituent groupswhich do not have a dye group attached thereto.
 7. An event sensor ofclaim 1 further including;and overcoating, said overcoating comprisingcellulose containing an opaque agent in said cellulose, said overcoatingcovering said matrix on said optical fiber.
 8. A pH sensor whichcomprises:an optical fiber, said optical fiber having an opticalsurface; a matrix of a regenerated cellulose formed in situ on saidoptical surface of said optical fiber by depositing a droplet ofcellulose in solution in a carrier solvent on said optical fiber andregenerating said cellulose from said solution by treating said carriersolvent with an acid solution regeneration reagent to form said matrixon said optical fiber; a plurality of substituent groups located on saidcellulose; a plurality of pH sensitive dye groups attached to saidcellulose by attaching each of said pH sensitive dye groups to one ofsaid substituent groups; and a plurality of substituent group blockinggroups located on essentially any of said plurality of substituentgroups which does not have a dye group attached thereto.
 9. The pHsensor of claim 8 wherein said substituent group blocking groupscomprise acylating groups.
 10. The pH sensor which comprises:an opticalfiber, said optical fiber having an optical surface; a matrix of aregenerated cellulose formed in situ on said optical surface of saidoptical fiber by depositing a droplet of cellulose in solution in acarrier solvent on said optical fiber and regenerating said cellulosefrom said solution by treating said carrier solvent with an acidsolution regeneration reagent to form said matrix on said optical fiber;a plurality of aminoalkyl groups located on said cellulose; a pluralityof pH sensitive dye groups attached to said cellulose by attaching eachof said pH sensitive dye groups to one of said aminoalkyl groups withsulfonylamido linkage, said plurality of pH sensitive dye groups beingless than said plurality of aminoalkyl groups
 11. A pH sensor whichcomprises:an optical fiber, said optical fiber having an opticalsurface; a matrix of a regenerated cellulose formed in situ on saidoptical surface of said optical fiber by depositing a droplet ofcellulose in solution in a carrier solvent on said optical fiber andregenerating said cellulose from said solution by treating said carriersolvent with an acid solution regeneration reagent to form said matrixon said optical fiber, said solution further containing glycerol in anamount effective to enhance the permeability of said matrix to ionicspecies; a plurality of substituent groups located on said cellulose;and a plurality of pH sensitive dye groups attached to said cellulose byattaching each of said pH sensitive dye groups to one of saidsubstituent groups.